UDC in subject gateways: experiment or opportunity?

The paper gives a short overview of the history of use of UDC in Internet subject gateways (SGs) with an English interface, from 1993 to 2006. There were in total, nine quality controlled SGs that were functional for shorter or longer periods of time. Their typology and functionality is described. Quality SGs have evolved and the role of classification has changed accordingly from supporting subject organization on the interface and automatic categorization of resources, towards supporting a semantic linking, control and vocabulary mapping between different indexing systems in subject hubs and federated SGs. In this period, many SGs ceased to exist and little information remains available regarding their status. SGs currently using UDC, for some part of their resource organization, do not use a UDC subject hierarchy at the interface and its role in resource indexing has become more difficult to observe. Since 2000, UDC has become more prevalent in East European SGs, portals and hubs, which are outside the scope of this research. This paper is an attempt to provide a record on this particular application of UDC and to offer some consideration of the changes in requirements when it comes to the use of library classification in resource discovery.